text: Aluminon, the triammonium salt of aurintricarboxylic acid, is a dye often used to detect the presence of the aluminium ion in an aqueous solution. Aluminon forms a red complex salt in combination with Al.
  In addition to its use in qualitative inorganic analysis, aluminon has applications in pigment production. It forms brilliantly colored lake pigments with many metals. The pigments are red in combination with Be and Ga. The pigment is deep purple or reddish-brown in combination with Fe. Color of a particular pigment in acidic solutions may change: aluminon and Sc form red pigments if the solution is acidic, but otherwise the solutions are colorless.
  Aluminon is prepared by reacting sodium nitrite with salicylic acid, adding formaldehyde, then treating with ammonia.